1. Field
The disclosed technology relates to systems that can process semiconductor substrates and, in particular, to systems for uniform metal plating.
2. Description of the Related Art
Processing of a semiconductor substrate, such as GaAs wafer, may include plating a metal layer, such as gold, over the semiconductor substrate. The metal layer may be applied over one or more features of the substrate, such as a via. It can be important for the plated metal layer to be uniformly applied over the features of the substrate. For example, a uniformly plated metal layer can have reduced resistance and inductance relative to a metal layer having a varying thickness.
The substrate to be plated may operate as a cathode of a plating circuit, and an anode of the plating circuit may include a metal to be plated on the substrate. The anode and the cathode may be immersed in a solution that can include one or more dissolved metals, along with other ions that may permit the flow of electricity. A power supply can supply a current to the anode, which may oxidize the metal atoms and allow the metal atoms to dissolve in the solution. The dissolved atoms may be reduced where the solution meets the cathode, such that they plate the cathode.
As wafer size increases, issues associated with plating a uniform metal layer over features in various positions across a major surface of a substrate may become exacerbated. Moreover, the time required for plating may increase for larger wafers, slowing down the overall process flow. Accordingly, there exists a need for improved apparatus and methods for uniform metal plating.